An excavating hoe which may be utilised in mining applications such as for clearing overburden from an accessible coal or mineral deposit has been described in Australian Patent 567437 (ie. which corresponds to U.S. Pat. No. 4,731,941). This prior art excavating hoe includes an upper body frame, a scraper blade pivotally attached to a rear end of the body frame, means for connecting the hoe to one or more draglines for moving the hoe in a forward direction and means for connecting the hoe to a tail line for moving the hoe in a rearward direction. The body frame has generally horizontally disposed top means for floating the body frame on a load of scraped material advanced by the scraper blade and the body frame has side means for loading and/or retaining the load of scraped material advanced by the scraper blade. In operation the scraper blade was pivoted to a material scraping position when the hoe was traversed in a forward direction and was reversely pivoted to a non-operative position when the hoe was traversed by the tail line in a reverse direction.
A conventional excavating hoe or bucket which may also be used in conventional draglines is also described in Australian Patent 576437.
Conventional draglines include a dragline housing which incorporates a hoist winch, an outwardly extending boom carrying a hoist cable connected to the hoist winch which may extend downwardly from an outer end of the boom attached to an excavator bucket as hereinafter described and a drag cable attached to the excavator bucket which is connected to a drag winch located in the dragline housing. Both the drag winch and hoist winch are suitably driven from electric motors and the dragline housing is suitably rotatably mounted to a support base by a central bearing. The dragline housing may be equipped with crawler tracks for locomotion or alternatively and more commonly is equipped with a walking mechanism having a pair of support feet which are reciprocatable relative to the dragline housing and thus may propel the dragline housing in a desired direction of travel.
The excavator bucket is usually arcuate in shape having a base and peripheral wall provided with an open front or access mouth whereby soil or overburden may gain access to the interior of the bucket as the bucket is dragged or moved through loose overburden by the drag cable(s). A plurality of ripper teeth along a free edge of the base may be provided in the open front or access mouth.
A rear end of the excavator bucket is provided with a pair of opposed support chains each attached to a respective support lug on the external face of the upper side wall. The chains may be interconnected by a horizontal bar.
There also may be provided a support loop or arch adjacent the open front of the bucket to which may be attached support cable(s) connected to the hoist cable(s) and also to the drag cable(s) by use of an appropriate sheave mechanism. There also may be provided a pair of drag chains attached to support lugs below the support arch.
The abovementioned conventional dragline operates to remove overburden or to mine a mineral from a valuable mineral or coal deposit such as a coal seam. After initially drilling and blasting the overburden by a suitable explosive such as ammonium nitrate, the overburden is loosened and softened. A bulldozer was then used to level a portion of the overburden to provide a flattened hill for supporting the dragline housing. The excavator bucket was then moved to the desired location wherein the drag winch was free spinning so that the drag cable was slack. In this movement the hoist winch has enough tension to hold the excavator bucket as it swings freely when suspended from the boom. Then the excavator bucket is placed on the ground by actuation of the hoist cable and tension is subsequent applied to the drag cables. The bucket is subsequently dragged through the loose overburden until it is full. The tension is then maintained in the drag cables and tension is applied to the hoist cables to elevate the full bucket above the overburden. By balanced control of me hoist winch and drag winch the bucket may then be moved towards the top of the boom which has a sheave for supporting the hoist cable. The dragline housing is then rotated away from the excavation site towards a spoil pile or dump from the overburden in the bucket and is tipped out of the excavator bucket by slackening of the tension in the drag cables. By appropriate control of the hoist cable the empty excavator bucket then assumes its normal orientation and is then moved back to the excavation site by rotation of the dragline housing.
While the abovedescribed excavating hoe or dragline bucket was generally satisfactory in operation, it was considered that operating efficiency of the hoe or bucket could be improved and one example of such efficiency was to provide an improved excavating hoe or bucket which could transport a greater load per unit of drag force.